1. Field of the Invention
The present invention relates to a light emitting semiconductor diode made of a III-V compound semiconductor, such as GaAs and Ga.sub.1-x Al.sub.x As.
2. Description of the Prior Art
In conventional light emitting diodes, light generated at a p-n junction formed in a semiconductor body and emitted toward one side of the p-n junction, where the forbidden band gap is wider than that at the p-n junction, can emerge from the semiconductor body into the air, and light emitted toward the other side of the p-n junction is absorbed or scattered by semiconductor material wherein the forbidden band gap is narrower than at the p-n junction and by an ohmic contact formed on a surface of the semiconductor layer and provides little or no contribution to the light output. This lowers the emission efficiency. Furthermore, another disadvantage is that heat generated at the p-n junction gives rise to a large temperature increase, which, in turn, lowers the internal quantum efficiency. An example of this type of light emitting semiconductor diode is described in U.S. patent application Ser. No. 612,282.
In order to reflect part of the light at the position of the ohmic contact, several new types of semiconductor diodes have been proposed. In one, an SiO.sub.2 layer deposited on the surface of the semiconductor body has a plurality of perforations. A metal electrode is deposited on the SiO.sub.2 layer and through the perforations on the surface of the semiconductor body and forms an ohmic contact. Part of the light emitted toward the ohmic contact is reflected by the SiO.sub.2 layer and enhances external quantum efficiency. In another diode, the surface of the semiconductor body has a plurality of grooves and a metal electrode is in contact with the surface only where no grooves are formed, so that part of light is reflected at the bottom of the grooves. These structures can enhance external quantum efficiency, but incident light nearly normal to the surface of the semiconductor body is reflected neither at the bottom of the grooves nor at the surface of the SiO.sub.2 layer. Another disadvantage is that the dissipation of heat generated at the p-n junction is as poor as that of conventional semiconductor diodes.